On @ The 90: NASA Re-Reaches for the Nuclear Future « AmericaSpace

This is an image of the completed
NERVA test stage. Image Credit:
NASA Found at: Encyclopedia
Astronautica www.astronautix.com

On @ The 90: NASA Re-Reaches for the Nuclear Future

By Christopher Paul

Research at the Marshall Space Flight Center has picked up on an old thread to advance rocket technology. Known as the Nuclear Thermal Rocket, this technology uses the heat generated by nuclear reactions to produce rocket thrust. As the space agency once again eyes destinations beyond the orbit of Earth, NASA must review sources of propulsion better suited for long-duration missions to distant destinations—and that means nuclear.

Normal chemical rockets used the heat generated by chemical reactions between fuels and oxidizers to create hot gas which is forced through a nozzle to produce thrust. Nuclear thermal rockets use the heat generated either by the radioactive decay of unstable isotopes or nuclear fission reactions to heat gas, force it through a nozzle, and create thrust. The key difference is that nuclear thermal rockets are more efficient at harvesting the energy of their heat source, and thus can produce higher thrust and greater exhaust gas velocities—two key measures of rocket performance. The Space Shuttle Main Engine’s combustion temperature is about 3500 K; while NASA-Marshall’s simulated NTR has a similar internal temperature, real NTRs can get much hotter, as hot as the materials that make them up can stand.